I. Field of the Invention
The invention pertains to rung-ladder attachments. More specifically, the invention pertains to a removable ladder step can be mounted on a rung-ladder for providing additional foot support. The device can also be used as a surface for holding tools or the like.
This invention is mainly intended for professionals spend extended period of time on a rung-ladder. This device improves work conditions and allows a user to save time and energy while standing on a ladder. Different techniques and materials were used to develop various ladder steps for providing an additional supporting area. The previous inventions are inconvenient, complex, unstable, heavy, costly or limited to be used with particular rung-ladders.
A ladder step should be wide enough to support a user's feet, stable, rigid, safe, capable of accommodating various leaning angles and/or various ladder types, readily mountable on a ladder, light in weight, relatively small in size for easy handling and positioning.
II. Description of the Prior Art
U.S. Pat. No. 8,657,070 to Richard O'Brien, Holly O'Brien, discloses a unitary step extension device comprising a standing surface extending between two (2) and three (3) inches and defining a pair of laterally opposed notches, a lip having at least one resilient stopper adapted to engage a rung, and a tube-shaped support having an engaging portion which engages two side rails. The lip of the unitary step is capable only of engaging a D-shaped rung because, mounting the unitary step on a round-shaped rung increases a moment arm which augments stresses in the lip and reduces strength. The removable ladder step of the present invention has neither lip nor notches, the present invention has a unique inclined rung-engaging wall extends from a base member to engage a rung, this has an advantage that the inclined rung-engaging wall acts in a direction that prevents a moment generation. This means that the rung-engaging wall resists only a tensile force which requires much lower strength in comparison to a moment action, as a result, the step of the present invention is capable of efficiently supporting a heavy load and engaging various rung types without affecting the strength or endangering safety. When installing the unitary step on a ladder, the lip engages the rung and the tube-shaped support engages the two side rails, the unitary step has no adjustment means for accommodating various side rail depths. The present invention has a unique pair of adjustable holding devices used to accommodate side rails having various depths. The tube-shaped support of the unitary step extends laterally beyond the standing surface to brace against the side rails, this feature makes the unitary step usable only with ladders that have a distance between a rear surface of a rung and a front face of a side rail equals to a distance between an interior surface of the lip and the engaging portion, this means that the unitary step can be only installed on certain types and/or sizes of ladders. In the present invention, a load-supporting structure is configured to be installed between two side rails so that the removable ladder step can be adjusted by the pair of adjustable holding devices. A horizontal standing surface, this feature is unachievable in the unitary step if the ladder includes side rails having a relatively small depth which creates a gap between the side rails and the engaging portion, the gape prevents a face to face contact which is essential to maintain the standing surface in a horizontal level. In the present invention, each one of the pair of adjustable holding devices has a rail spacer configured to adjust a standing surface relative to a horizontal plane. The unitary step offers a relatively small standing surface width because, increasing the width increases stresses generated in the lip which could cause the lip to fail. The unique configuration of the load-supporting structure allows the present invention to offer a standing surface having more convenient width. Further, the base member configured to have a rigid structure located in a position that prevents stresses from being concentrated in certain areas, the advantage of the base member is to increase the load bearing capacity of the removable ladder step.
U.S. Pat. No. 6,966,406 to Edward Lee Nash, discloses a step platform can only be used with a hollow rung ladder having open ends. The step platform extends wider than the side rails. A supporting rod extends beyond the side rails. Increasing the length of the step platform generates higher bending moment in the supporting rod. The present invention provides a unique rigid configuration of a base member, a front wall and a rung-engaging wall.
CA patent 2,028,158 to Nowlan, comprises a vertical supporting member to secure the platform to a pair of rungs.
CA patent 1,176,610 to Stecklow combines a supporting platform with a telescopically adjustable stabilizer.
U.S. Pat. No. 4,482,030 to Lincourt is for a safety platform with L-shape hooks used for attachment to the upper and lower rungs.
U.S. Pat. No. 1,920,552 to Dollerhide discloses a detachable ladder step secured to two rungs of a ladder; U-shape hooks are used for securing the ladder step to the upper rung.
U.S. Pat. No. 3,511,338 to Chapman discloses a U-shape bracket used to secure the apparatus to a lower rung and steel hooks to secure the stand to an upper rung.
U.S. Pat. No. 2,500,559 to Miller is directed to a ladder platform wherein a base is pivotally secured to one rung, with swinging hook means are adjustable to various positions, by means of notched formations inside flanges of the platform.
U.S. Pat. No. 3,294,197 to Kwiatkowski discloses a perch for a ladder that sits upon one rung and has a cross member which engages vertical support arms.
U.S. Pat. No. 4,646,878 to Moyer discloses a portable ladder step mountable on two rungs.
U.S. Pat. No. 4,401,187 to Van Patten discloses a ladder platform accessory using resilient bracket arms in a hinged connection to the platform.
U.S. Pat. No. 4,211,307 to Ethridge discloses a removable step for a ladder which permits the shelf or platform to be pivoted inward and outward so as not to obstruct normal use.
U.S. Pat. No. 3,067,836 to Carnicelli is directed to an adjustable step for ladders utilizing two side members which contact the ladder rungs.
U.S. Pat. No. 2,297,883 to Glover, U.S. Pat. No. 2,282,133 to Horton, U.S. Pat. No. 4,687,075 to Skaggs and U.S. Pat. No. 1,725,723 to Silva are variations of the Carnicelli type of construction.
U.S. Pat. No. 1,216,214 to Connell is also analogous to the construction type of Carnicelli.
U.S. Pat. No. 4,909,351 to Johnson, discloses a platform attachment for a ladder with both a retracted and a working position.
Taking into consideration the above mentioned features, none of the previous inventions, whether taken singly or in combination, discloses or suggests the particular characteristics of the present invention as claimed.
A need exists, therefore, for a novel removable ladder step that is rigid, compacted, stable and economic. The present invention provides further advantages as described in the following summary.